1. Chapter 4
Orthographic
Writing

2. TOPICS
Views selection
Alignment of views
Orthographic writing steps
Basic dimensioning
Tangency and intersections

3. View Selection

4. VIEW SELECTION STEPS
1. Orient the object to the best position relative to a glass box.
2. Select the front view.
3. Select adjacent views.

5. STEP 1 : Orient the Object
The object should be placed in its natural position.
The object should presents its features in actual size and shape in orthographic views.
GOOD
NO !

6. STEP 2 : Select a Front View
The object’s longest dimension should be presented as a width.
First choice
Second choice
Waste more space
Inappropriate
GOOD

7. STEP 2 : Select a Front View
The adjacent views that are projected from the selected front view should appear in its natural position.
Inappropriate

8. STEP 2 : Select a Front View
Choose the view that have the fewest number of hidden lines.
GOOD
Inappropriate

9. STEP 3 : Select an Adjacent View
Choose the view that have the fewest number of hidden lines.
GOOD
Inappropriate
GOOD
Inappropriate

10. STEP 3 : Select an Adjacent View
Choose the minimum number of views that can represent the major features of the object.
Necessary
Hole’s location can be specified on the same view.
Easy to understand
Difficult to interprete.
Necessary

11. STEP 3 : Select an Adjacent View
Choose the views that are suitable to a drawing space.
POOR
Not enough space
for dimensioning.

12. STEP 3 : Select an Adjacent View
Choose the views that are suitable to a drawing space.
GOOD

13.       Example : View selection mislead to… Size descriptionH W
F.V. H W D
F.V. & T.V.
Three views
F.V. & R.S.V.   
Size description   
Shape description

14. ONE-VIEW DRAWING Flat part having a uniform thickness. Unnecessary
These 2 views provide only information about the part thickness !

15. ONE-VIEW DRAWING Cylindrical-shaped part. Unnecessary Repeat !
Infer from CL
Unnecessary

16. TWO-VIEW DRAWING
There exists an identical view.
Repeat !
Unnecessary

17. TWO-VIEW DRAWING
The 3rd view has no significant contours of the object.
Unnecessary

18. TWO-VIEW DRAWING
The 3rd view has no significant contours of the object.
Unnecessary

19. Alignment of Views

20. PROJECTION SYSTEMS 1. First angle system 2. Third angle system
- European country - ISO standard
First Quadrant
2. Third angle system
- Canada, USA, Japan, Thailand
Third
Quadrant

21. ORTHOGRAPHIC PROJECTION
1st angle system
3rd angle system

22. ORTHOGRAPHIC VIEWS 1st angle system 3rd angle system   Folding line

23. ORTHOGRAPHIC VIEWS 1st angle system 3rd angle system Top View
Right Side View
Front View
Top View
Front View
Right Side View

24. PROJECTION SYMBOLS
First angle system
Third angle system

25. PROJECTION SYMBOLS
Suggested proportion d
1.7d
2.2d

26. Orthographic Writing Steps

27. WRITING STEPS
1. Select the necessary views
2. Layout the views.
3. Project the views.
4. Dimension the views.

28. 1. SELECT THE NECESSARY VIEWS
TOP
FRONT

29. 2. LAYOUT THE VIEWS 1:1 A4 Choose an appropriate scale 152 64 25 45

30. PROJECT THE VIEWS

31. DIMENSION THE VIEWS x x z y y x x y y PART NAME NOTES
1. Dimensions in millimeters.
2. ….

32. TRANSFERING THE DEPTH DIMENSION
1. Direct measurement 1 2 3 27 1 2 3
Starting point 27

33. TRANSFERING THE DEPTH DIMENSION
2. Use miter line
45
Views too close

34. Basic Dimensioning

35. COMPONENTS 1. Extension lines 2. Dimension lines 3. Leader lines10 27
10 Drill, 2 Holes
R16
2. Dimension lines
3. Leader lines
4. Dimension numbers 17
5. Local notes 43

36. Tangencies and Intersections

37. TANGENT & INTERSECTION
No line is formed when curved surface tangent to a plane surface.
Line is formed when curved surface intersects a plane surface.
No line
tangent
intersect
No line
tangent
intersect

38. TANGENT & INTERSECTION
limiting element
tangent
tangent
tangent
plane
intersect

39. TANGENT & INTERSECTION
No line
tangent
tangent
tangent
tangent
No line
tangent
No line

40. QUIZ

41. 1. Which should be the natural position of the light bulb ? (20 sec)5 10 15 20

42. 2. Which are the necessary views ? (60 sec)
A-C-E
E-B-D
E-A
E-C A B C D E F 15 30 45 60

43. 3. Which is in correct first angle projection ? (180 sec)b) c) d) 45 90
135
180

44. 4. Which is in correct third angle projection ? (180 sec)b) c) d) 45 90
135
180

45. 5. Which is a wrong 3rd angle orthographic views ? (180 sec)b) c) d) 45 90
135
180